1. Field of the Present Invention
The present invention relates to a semiconductor apparatus comprising a circuit including a thin film transistor (hereinafter, referred to as a TFT) and a method for manufacturing the semiconductor apparatus. For example, the present invention relates to an electro-optical device typified by a liquid crystal display panel, an EL (an electroluminescence) display device, an EC display device, and the like. In addition, the present invention relates to an electric device for improving processing rate formed by using the TFT, for example a central processing unit (CPU), and a method for manufacturing the electric device. Further, the present invention relates to an electric apparatus equipped with these electro-optical device and electric device as the components.
2. Description of the Related Art
In recent years, a thin film transistor (TFT) is formed using a semiconductor film formed over a substrate having an insulating surface, and a semiconductor apparatus having a large-sized integrated circuit formed of the TFT has been developed actively.
In the semiconductor apparatus having such a large-sized integrated circuit, each device for forming the semiconductor apparatus is miniaturized and integrated.
Therefore, it has become much more important to perform, for example, a process of forming a multilayer wiring after forming the TFT, as the devices are miniaturized and integrated. In the process of forming a multilayer wiring, a series of process of forming an insulating film after forming the TFT, forming a contact hole, and forming a wiring is repeated.
In this process of forming a multilayer wiring, a contact hole is usually formed in an insulating film by performing the processes of forming, patterning, and etching an insulating film.
However, it is apparent that a phenomenon to damage the insulating film occurs when this contact hole is formed (for example, see Reference 1, Japanese Patent Laid-Open No. H5-166945).
Dry etching and wet etching can be considered as the method for forming the contact hole in the insulating film. However, in order to form a minute contact hole as the size of the devices is miniaturized, it is general to employ dry etching using plasma.
However, there is a fear that the transistor characteristic of the TFT is deteriorated by physical damage, charge up damage, damage due to X-ray or ultraviolet radiation, or the like during dry etching.
In particular, when plasma is generated for etching, charged particles of an electron, an ion, or the like is injected into a gate electrode or gate wiring, or a source electrode or drain electrode of the TFT through the insulating film at the time of forming the contact hole in the insulating film over the TFT. When the contact hole is formed in an interlayer insulating film in a multilayer wiring structure, the charged particles are injected no matter how the interlayer insulating film is formed in an upper layer of the TFT. For example, when the contact hole is formed in a first interlayer insulating film being in direct contact with the TFT, the charged particles are injected into the gate electrode or gate wiring, or the source electrode or drain electrode. In addition, when a second wiring connected to the gate electrode or gate wiring, or the source electrode or drain electrode is formed over the first interlayer insulating film and a second interlayer insulating film is formed over the second wiring, the charged particles are injected into the second wiring at the time of forming the contact hole formed in the second interlayer insulating film. Further, since the second wiring is connected to the gate electrode or gate wiring, or the source electrode or drain electrode, the charged particles are injected into up to the gate electrode or gate wiring, or the source electrode or drain electrode through the second wiring. In other words, when the contact hole is formed, the charged particles are injected into up to the gate electrode or gate wiring, or the source electrode or drain electrode by operating the wiring placed in the lower layer as an antenna. Then, the charged particles that reaches the gate electrode or gate wiring, or the source electrode or drain electrode generates potential difference between the gate electrode or gate wiring and a source (or drain) region of the TFT. Therefore, an electric field is applied to a gate insulating film and the gate insulating film is given damage of dielectric breakdown when this electric field is strong. Although there is no breakdown of the gate insulating film, the transistor characteristic is deteriorated, for example, the threshold voltage of the TFT is shifted, or the variation in characteristic is increased.
In addition, this deterioration of the transistor characteristic is more apparent in the TFT having a minute structure.
This is because the injected charged particles are concentrated in a small area and the electric field generated in the gate insulating film becomes larger. Therefore, the damage to a TFT is heavier in the TFT having a minute structure.